SURGICAL RESECTION OF LARGE INCOMPLETELY TREATED INTRACRANIAL ARTERIOVENOUS-MALFORMATIONS FOLLOWING STEREOTAXIC RADIOSURGERY

Although radiosurgery is effective in obliterating small arteriovenous malformations (AVMs), it has a lower success rate for thrombosing lar ger AVMs. The authors surgically resected AVMs from 33 patients rangin g in age from 7 to 64 years (mean 30.4 years) 1 to 11 years after radi osurgery. Initial AVM volumes were 0.8 to 117 cm(3) (mean 21.6 cm(3)), and doses ranged from 4.6 to 45 GyE (mean 21.2 GyE). Of 27 AVMs in el oquent or critical areas, 10 were located in language, motor, sensory, or visual cortex, 11 in the basal ganglia/thalamus, one each in the b rainstem, hypothalamus, and cerebellum, and three in the corpus callos um. Venous drainage was deep in 13, superficial in 1?, or both in eigh t lesions. Spetzler-Martin grades were II in one, III in 12, IV in 16, and V in four patients. Eight patients experienced rebleeding after r adiosurgery but prior to surgery. Three patients developed radiation n ecrosis and 25 underwent endovascular embolization prior to surgery. A t surgery the AVMs were found to be markedly less vascular, partially thrombosed, and more easily resected, compared to those seen in patien ts who had not undergone radiosurgery. Pathological investigation show ed endothelial proliferation with hyaline and calcium in vessel walls. There was partial or complete thrombosis of some AVM vessels and evid ence of vessel and brain necrosis in many cases. Complete resection wa s achieved in 28 patients and partial resection in five. Clinical outc ome was excellent or good in 31 cases, and two patients died of reblee ding from residual AVM. Four patients' conditions worsened following m icrosurgical resection. Final clinical outcome was largely related to the pre-treatment grade. Radiosurgery several years prior to open micr osurgery may prove to be a useful adjunct in treating unusually large and complex AVMs.